I popped this plus the two other stacked achievements by a glitch. In the third set of levels, "extreme skies", level 21, "Pick one", at the first set of rails, go to the right or left, doesn't matter, jump at the end of the rail (needs some practice to get forward momentum) and fly above and beyond the next rail. I ended up falling, falling, but I never got the "Out of bounds". So I just did different grabs and flips until I had racked up enough points, and then let go. Boom, 3 cheevos, easy as that! I've repeated the glitch several times both to the left and right. Anyone that can confirm that it is a general glitch, working for you as well?